1. Field of the Invention
The present invention relates to a method and an apparatus for inspecting foreign matters in or on repeated micro-miniature patterns, in particular, to the method and the apparatus for use in inspecting or detecting minute or microscopic foreign matter(s) upon a surface of an object to be inspected, such as the repeated micro-miniature patterns which are formed on a semiconductor wafer, with high sensitivity.
2. Description of Related Art
With great advance in scale of integration and in miniaturization of circuitry patterns of a semiconductor integrated circuit (herein after, it is called only by xe2x80x9cICxe2x80x9d) in recent years, circuit patterns being formed on it come to be in an order of 1 xcexcm or less than that in width thereof. For producing such an IC with high productivity, it is necessary to detect particles or foreign matters attached on the surface of the wafer and to inspect or examine sizes, shape, feature and property thereof, so as to quantitatively obtain cleaning degrees in various apparatuses and/or processes for producing the semiconductor, and thereby to manage production process appropriately. Therefore, conventionally, the detection and/or inspection of the foreign matters on wafers was applied to, with methods and/or apparatuses for inspection of foreign matters attached or adhered to the wafers, as works in IC production facilities in factories, so as to manage the production processes appropriately.
The conventional inspection apparatuses for inspection of foreign matters on wafers can be divided roughly into two categories. A first one is a patterned wafer inspection apparatus of an image comparison type (hereinafter, it is called by a xe2x80x9cvisual inspection apparatusxe2x80x9d), in which the comparison is carried out between the image under a bright field of an illumination and a reference pattern which is previously stored. A second one is a patterned wafer inspection apparatus of such type (hereinafter, it is called by xe2x80x9can inspection apparatusxe2x80x9d) that it detects scattered light in a dark field under an inclined illumination, acknowledges existence of defects or foreign matters, and determines coordinate positions and the number thereof, by means of the coordinates obtained at the time of detection of the scattered light.
Further, an example of such apparatuses for inspection of defects on the wafers is described on pages from 97 to 116 of xe2x80x9cNikkei Micro-devices, March, 1997xe2x80x9d, which is published by Nikkei Business Publication, Inc.
The visual inspection apparatus mentioned above has an advantage that it shows high accuracy in inspection; however, it has drawbacks that throughput thereof is low and that it is expensive in price. And, since an image or visual data can be obtained by the visual inspection apparatus, it enables a so-called review (i.e., a confirmation or an inspection by means of the image, visually). However, by the inventors of the present invention, it is made clear that, in the visual inspection apparatus, information not only necessary but also unnecessary to be reviewed are also provided too much, in comparison with the number of pieces of the wafers to be inspected, including such as for a microscopic defect, therefore, a probability of obtaining fatal or killer defects is very low and there is a drawback that an efficiency of the review comes to be low.
On the contrary, though the inspection apparatus mentioned above has a drawback that it is lower than that of the visual inspection apparatus in the accuracy, it has an advantages that the throughput of it is higher, comparing to that of the visual inspection apparatus, and that it is also lower in the price thereof. And, since the data which can be obtained from the inspection apparatus includes only the coordinate positions of the defects in a surface area of the wafer, as well as an intensity of the scattered light, therefore, it is impossible to obtain information relating to the size(s) of the defect (i.e., a diameter of the particle) and the shape thereof (even if possible, within a degree to classify it into S (small), M (medium) and L (large) in the size, roughly). Accordingly, for obtaining the information concerning to those in more detail, there is a necessity of using the inspecting apparatus of analyzer type, such as the visual inspection apparatus as mentioned above or an another kind of inspection apparatus, such as a SEM (Scanning Electron Microscope) which, however, takes a long time for inspection or analysis and expensive in the price.
An object, according to the present invention, is to provide a method and an apparatus for inspecting foreign matters, which can obtain such the fatal defects with a good efficiency, and is also able to inspect the sizes and the shapes thereof.
According to the present invention, for achieving the object mentioned in the above, first of all, there is provided a method for inspecting foreign matter in repeated micro-miniature patterns formed upon a surface of an object to be inspected, comprising following steps:
irradiating an inspection light directed upon the surface of the object to be inspected, on which the repeated micro-miniature patterns are formed, with an inspection light irradiating device;
detecting scattered light of the inspection light being scattered upon the surface of said object to be inspected with a scattered light detector;
determining a coordinate position of a foreign matter upon the surface of said object to be inspected, on a basis of the detection of said scattered light in the above step;
picking up an image of said foreign matter which is determined with the coordinate position thereof, under a bright field illumination by an irradiation means, at a coordinate position which is corresponding to that in said scattered light detecting step; and
deciding said foreign matter at least one of in size, shape, color and property thereof, depending upon an image of said foreign matter which is extracted on a basis of said picking up of the image obtained in the above step.
Further, according to the present invention, for achieving the object mentioned in the above, there is provided an apparatus for inspecting foreign matter in repeated micro-miniature patterns formed upon a surface of an object to be inspected, comprising:
an inspection light irradiating device for irradiating an inspection light directed upon the surface of the object to be inspected, on which the repeated micro-miniature patterns are formed;
a scattered light detector for detecting scattered light of the inspection light being scattered upon the surface said object to be inspected;
means for determining a coordinate position of a foreign matter upon the surface of said object to be inspected, on a basis of the detection of said scattered light;
an irradiation means for applying a bright field illumination upon the surface of the object to be inspected, on which the repeated micro-miniature patterns are formed;
means for picking up an image of the foreign matter which is determined with the coordinate position thereof, under a bright field illumination by said irradiation means, at the coordinate position which corresponding to that which is determined by said coordinate position identifying means; and
means for deciding the foreign matter at least one of in size, shape, color and property thereof, depending upon an image of the foreign matter which is extracted on a basis of said picking up of the image obtained by said image picking up means.
And, further according to the present invention, there is also provided an apparatus for inspecting foreign matter, as defined in the above, further including:
means for obtaining a reference image by picking up the image of the micro-miniature pattern, under a bright field illumination, at an another coordinate position on the surface of said object to be inspected, which is corresponding to but different from the coordinate position which is determined by said determining means; and
means for obtaining an arithmetic process image between said object image and said reference image, wherein said decision means decide a presence of a defect at the determined coordinate position on said object to be inspected, which is previously designated, on a basis of the arithmetic process image obtained by said arithmetic process image obtaining means.
Furthermore, according to the present invention, for achieving also the object mentioned in the above, there is provided an apparatus for inspecting foreign matter in repeated micro-miniature patterns formed upon a surface of an object to be inspected, comprising:
an inspection light irradiating device for irradiating an inspection light directed upon the surface of the object to be inspected, on which the repeated micro-miniature patterns are formed;
a scattered light detector for detecting scattered light of the inspection light being scattered upon the surface said object to be inspected;
means for obtaining a first information related to a foreign matter attaching upon the surface of said object to be inspected, which is obtained on a basis of the detection of said scattered light by said scattered light detector;
an irradiation means for applying a bright field illumination upon the surface of the object to be inspected, on which the repeated micro-miniature patterns are formed;
means for picking up an image of said foreign matter, under a bright field illumination by said irradiation means;
means for obtaining a second information related to said foreign matter depending upon the image of the foreign matter, which is obtained on a basis of said picking up of the image by said image picking up means under the bright field illumination; and
means for displaying said first information and said second information on a display screen thereof.
And, according to the present invention, for also achieving the above-mentioned object, there is provided a method for inspecting foreign matter in repeated micro-miniature patterns formed upon a surface of an object to be inspected, comprising following steps:
obtaining an object image by picking up the image of the micro-miniature pattern, under a bright field illumination, at a coordinate position on the surface of said object to be inspected, which is designated previously;
obtaining a reference image by picking up the image of the micro-miniature pattern, under a bright field illumination, at an another coordinate position on the surface of said object to be inspected, which is different from but corresponding to said coordinate position mentioned in the above step;
obtaining an arithmetic process image between said object image and said reference image; and
deciding of a presence of a foreign matter at the coordinate position on said object to be inspected, which is previously designated, on a basis of a condition of said arithmetic process image obtained in the above step.